"Having no trouble to walk backward, to run, to hop as a child, to climb a
steep mountain path, to restore balance after been tripped up by something,
to ride a bicycle, and at the same time not being able to walk normal;
people can hardly believe it is possible. People who have seen many PD's
believe it only because they want to trust their eyes. When I was in
hospital to be diagnosed and I was walking backward jokingly saying: "
maybe the only thing I need is a driving mirror", nurses said it was at
that place not an original joke at all.
Nobody really understands these phenomena. I remember how strange it was,
being very tense and not able to relax, as soon as I walked backwards or
downstairs I immediately felt normal. While in hospital I walked friends
who visited to the door, had trouble to reach the stair and than came down
quick and flexible. I saw the disbelief in the eyes of others. And maybe
for this reason it is not much talked about on this list because PWP's
hardly believe it themselves."
Ida Kamphuis, 52/12+
Holland
The above message is part of a larger message sent by Ida Kamphuis. While I
cannot explain these phenomena on a neurophysiologic bases, allow me to be so
audacious as to suggest that I believe I can explain them at the functional
level.
I would suggest that the reason we can walk backwards and the reason we can walk
up or down stairs is the same. This is because both of these manuevers
eliminate the fear factor. A PD subject who is undermedicated has an
attenuated stride length - sometimes as little as 2 or 3 inches (indeed
sometimes none at all). Walking forward requires an anterior displacement of
ones center of gravity beyond the fall point. A normal person knowing that he
has an adequate stride length availble will perform this manueuver fearlessly.
The PD person is inhibited by an overwhelming feeling of an impending fall
should he displace his center of gravity beyond the fall point. This is a
consequence of a perceived inability to extend the leg far enough or fast enough
to catch himself. Walking on stairs is a means of ambulating without the
necessity to displace one's center of gravity - one can essentially remain
upright while walking on stairs. Similarly, backwards walking is also near
upright walking - anatomically we cannot bend backwards at the waist. Stair
walking is particularly potent because in addition to the fear factor I would
sugget that there is a perception pathology in PD which makes it very difficult
to process low velocity motion. The horizontal pattern of the stairs serve as
visual cues. They essentially function as regular reference makers on the
real world and augment optical flow, much in the same way that apparent motion
is augmented when one sees the whilte dotted lines on a highway appear to move
as we drive over them. In this way the PD'er can compensate for his perceptive
impairment. Running is no problem because optical flow is accelerated beyond
the threshhold of perceptive pathology. And finally the abilty to escort a
companion to the door but not be able to return without assistance is a
cognitive means of controlling gait and is what I term droid-walking. An
akinetic person will often be able to walk if he synchronizes his stride to that
of a normal walking person.
Complex motor programs such as walking are actually an assemblage of simpler
tasks. This ability to bundle component motor packages into a more complex one
is a functon of basal ganglia. Thus, it is not unusual for secondary benefits
such as clarity of thinking, relaxation of tension and improved speech to occur
once the PD'er gets walking under visual cues.
